In a two-way communication system, and particularly in a two-way messaging system; the coverage area is often divided into regions or zones. Such a zoned communication system advantageously allows frequency reuse for improved radio frequency spectrum efficiency. A communication system, divided in such a manner must either know beforehand the location of a subscriber to deliver a message thereto, or the system must search the entire coverage area for the subscriber before the message can be delivered. The search process can delay the delivery of the message. During periods of high traffic the delays can become unacceptable to some users. To facilitate the locating of subscribers, conventional systems have been designed such that subscriber units monitor the communication channel to detect movement from one zone to another zone and to automatically register with the new zone when a zone boundary crossing is detected. During periods of high traffic and high subscriber mobility the traffic generated by the registration requests can load a system to the point where long delays in message delivery are experienced. Zone crossing detection and automatic registration also is troubled with nuisance registrations from subscribers located stationary on a zone border, where because of signal fading, the zone crossing detection process can toggle between zones.
Thus what is needed is a method and apparatus for limiting the zone border crossing registrations, and nuisance registration requests from subscribers located stationary on a zone border. What is also needed is a method and apparatus for prioritizing border crossing registration of high usage subscribers, thereby minimizing the number of system wide searches.